EP 0 623 798 A2 describes a plate heat exchanger having basin-shaped heat exchanger plates stacked one upon the other, the circumferential edges of which bear against each other and are soldered to each other in a leakproof manner, wherein all the heat exchanger plates have the same shape. In such designs, the lowest basin-shaped plate which is attached to the end plate forms the weakest member with regard to strength. The notch which arises in conventional structures between the lower basin-shaped plate and the end plate is particular unfavourable in terms of strength and the introduction of forces.
Oil coolers of this type are generally fastened at the end plate to the engine block or to modules close to the engine by means of screw-fastenings and are therefore subject to high transverse acceleration forces due to the engine vibrations during operation of the engine. A generally more important load results from the pulsing oil pressure in the lubrication system. This acts both from the inside in the individual oil sites and from below on the connecting plate. The module or engine housing opposite is usually configured at the interface with relatively long, open oil ducts which are closed by means of a contoured seal and the heat exchanger end plate. The heat exchanger connecting plate is loaded to bending by the prestress of the seal and in particular by the increasing oil pressure in the connecting ducts.
Plate heat exchangers of the above-mentioned type do not generally withstand such loads; the above-mentioned notch is often the starting point for cracks in the lowest oil plate or in the solder. The result is leaking and loss of media.
DE 197 11 258 C2 discloses a plate heat exchanger for a motor vehicle engine which consists of a plurality of basin-shaped plates which are stacked in a spaced apart manner and soldered to form adjacent hollow chambers with their upright edges lying inside each other, with the lowest plate being attached to an end plate. In order to meet strength requirements for mounting directly on the engine block, a reinforcement plate is also arranged between the end plate and the lowest plate, which reinforcement plate is provided with a border which encloses the edge of the lowest plate. The reinforcement plate is soldered to the lowest plate.
WO 2007/038871 A1 describes a plate heat exchanger having an end plate and a stack of basin-shaped plates, the lowest plate resting over its entire area on the end plate. The lowest plate is surrounded by a circumferential reinforcement frame.
If these reinforcement measures are not sufficient, the end plate, which is usually configured as a punched sheet metal part, is dimensioned to be correspondingly stronger, which however increases the space requirement, weight and costs.